# Defining Functions

Functions in C allow you to encapsulate a block of code, making the code modular and promoting reusability. Let's explore how to define and use functions in C.

## Function Definition

A function in C is defined using the following syntax:

```c
return_type function_name(parameters) {
    // Function body
    // Code to be executed
    return value; // Optional return statement
}
```

* `return_type`: The type of the value the function returns. It can be `void` if the function doesn't return a value.
* `function_name`: The name of the function.
* `parameters`: The input parameters that the function takes (if any).
* `return value`: The value the function returns (if applicable).

Here's an example of a simple function:

```c
#include <stdio.h>

// Function definition
void greet() {
    printf("Hello, world!\n");
}

int main() {
    // Function call
    greet();
    return 0;
}
```

In this example, the `greet` function is defined with a `void` return type, meaning it doesn't return any value. It prints "Hello, world!" when called from the `main` function.